My 80 300D sunroof won't work at all with power, it will work with the hand tool, I check the motor and gear box that fine, on top I oil the rails found some hard rubber black about a 1/2" long by the rails on both side don't know what they are from Thanks Ken

 

got picture of it?
better include your VIN too. i can tell you maybe.

 

the vin is 12313012206146 no photo it a 1980 300D The sunroof will work useing the hand tool but not under power the motor is good the gear box is good it seem to turn a bit hard with the hand tool but I never had a car like this so can't say for sure